Which of the following was the primary trade route along which buddhism spread?

Buddhism had spread across Asia through paths of overland and nautical routes between India, Southeast Asia, Central Asia, and China.  Secretive foreign monks who had traveled between India and China along the Silk Road were the majority responsible for the transmission of Buddhism at consistent levels.

"germany's geographic location was an advantage when it was on the offensive in the war because it was situated next to an extremely wide river, the rhine, which was difficult for the allies to cross."